OperationalError: (1054, "Unknown column 'inf' in 'field list'")

[teeberg]

Steps to reproduce

1. Create a table like this:

CREATE TABLE `test` (
  `test` float DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

2. Try to insert a very large float number:

import MySQLdb
db = MySQLdb.connect(user='test',passwd='test', db='test')
c = db.cursor()
c.execute('show tables')
c.execute('insert into `test` (`test`) VALUES (%s)', [2e2400])

Expected behavior

Since MySQL can't represent infinity and this could result in unexpected data issues (imagine somebody had inf or nan columns), I think it should raise a more descriptive error message saying that infinity is not a valid value.

Actual behavior:

Python exception:

---------------------------------------------------------------------------
OperationalError                          Traceback (most recent call last)
<ipython-input-9-2f445a32ed23> in <module>()
      3 c = db.cursor()
      4 c.execute('show tables')
----> 5 c.execute('insert into `test` (`test`) VALUES (%s)', [2e2400])

.../.venv/lib/python2.7/site-packages/MySQLdb/cursors.pyc in execute(self, query, args)
    248         except Exception:
    249             exc, value = sys.exc_info()[:2]
--> 250             self.errorhandler(self, exc, value)
    251         self._executed = query
    252         if not self._defer_warnings:

.../.venv/lib/python2.7/site-packages/MySQLdb/connections.pyc in defaulterrorhandler(***failed resolving arguments***)
     48     del connection
     49     if isinstance(errorvalue, BaseException):
---> 50         raise errorvalue
     51     if errorclass is not None:
     52         raise errorclass(errorvalue)

OperationalError: (1054, "Unknown column 'inf' in 'field list'")

Setting a breakpoint reveals that it's trying to run this query:

'insert into test (test) VALUES (inf)'

which is not valid, since MySQL doesn't know about inf.

What's going on?

Float2Str receives inf (huge float) as value and tries to interpolate it using

'%.15g' % o

which returns literally inf.

Not sure if that's something you'd like to fix here, but since it's producing an invalid MySQL query, I'd say it's a bug in this library.

How do you feel about checking for inf/nan and raising some kind of Exception?

Happy to submit a PR if we can agree on a good solution. :)

[methane]

I'm OK to raise DataError for inf and nan.
Please submit same PR to PyMySQL to keep both project shares same code as possible.